Heat losses due to thermal bridging are becoming increasingly relevant as more strict laws and energy awareness lead to greater insulation levels in walls, roofs, and floors. The relevance of thermal bridging has grown as homes have become well-insulated. Thermal bridging may substantially impact a dwelling’s overall thermal performance in particularly well-insulated homes. According to recent studies, thermal bridging has been responsible for up to 30% of a home’s heat loss. The heat loss caused by these thermal bridges is represented as a linear thermal transmittance (-value) – pronounced ‘p-value.
The surface temperature factor (f) is also determined as part of the evaluation method and is used to assess the danger of mold growth, which can have serious health consequences. Molds generate allergens (chemicals capable of causing an allergic reaction), irritants, and potentially poisonous substances. Mold spores can produce allergic reactions such as sneezing, runny nose, red eyes, and skin rash if inhaled or touched. Molds can also be the source of asthma episodes and other respiratory diseases. Thermal bridges occur within the building fabric in which heat fluxes are two or three-dimensional due to the presence of high conductivity materials. In many cases, basic calculations are no longer adequate to predict thermal performance accurately, and the construction must be analyzed using numerical modeling. Several numerical modeling software programs specify the model’s geometry, materials, and boundary conditions in two or three dimensions as suitable.
The current BRE BR 497 publication (Conventions for calculating linear thermal transmittance and temperature factors) details the conventions that thermal modelers should follow to produce consistent, reproducible results and thus contribute to the push for ambitious energy improvements in healthier buildings. The patterns concern using thermal modeling software to analyze the thermal performance of building junction details, goods, or parts as intended.
A thermal bridge is a scenario in which there is a direct link between the inside and outside of a structure through one or more parts that are more thermally conductive than the rest of the building envelope. Simply put, thermal bridging happens when a relatively small section of your heat loss envelope (the surfaces of your home exposed to the cold) has a much lower insulation value than the area surrounding it. First, consider having exterior wall insulation on the outside of your house, which would give enough comfort on the inside. Next, consider driving a steel nail through all that insulation and into the masonry beneath. This is a simple illustration of a thermal bridge – heat loss will occur quickly via the steel nail into the external environment, creating chilly patches within the house.
Thermal bridging in modern structures can develop as a result of poor design or execution. This is prevalent where construction elements penetrate the insulated fabric, such as around windows, or where the structure enters the building envelope, such as around balconies. The apparent solution is to install similar insulation to that used elsewhere in the home to address the issue. However, the nature of the problem frequently prevents this, such as when it happens on a window reveal with a limited area. If feasible, consider putting even a tiny layer of insulation. You may also consider adding humidity-controlled ventilation or decreasing moisture vapor by installing low-flow shower heads.
Reducing and restricting thermal bridging in buildings generally reduces energy requirements for the establishment, resulting in lower energy costs! It will also ensure that the building’s residents are healthier and hence happy in the long term. Thermal bridging occurs when a tiny section of a wall, floor, or roof loses much more heat than the surrounding region. Thermal bridging may happen in any form of structure. However, thermal bridging can cause increased heat loss, occupant discomfort, unexpected expansion/contraction, condensation, freeze-thaw damage, and associated moisture and mold problems in moisture-sensitive materials. The magnitude of these impacts determines the severity of the thermal bridge.
Effects
Thermal bridges may have the following effects:
Increased heat loss through the wall, resulting in higher operating costs, unexpected expansion and contraction or hot spots on the interior at thermal bridge locations, causing occupant discomfort and, in some cases, and health and safety issues. All thermal bridges do not cause these severe consequences. The design can then be corrected using the appropriate measurements. While there are some situations when thermal bridging cannot be repaired, providing continuous insulation is the most effective approach to counteract it.
The problem is that thermal bridging is a design fault inherent in cathedral ceilings. The best approach to combat thermal bridging in a cathedral ceiling is to install continuous insulation on both sides of the ceiling’s trusses. Unfortunately, this is frequently not done when the structure is built, making a retrofit a somewhat intrusive operation. In the end, most homeowners opt to skip the invasive process and insulate the stud holes.
